The induction of cellular immune responses to antigens prepared from oral bacteria associated with periodontal disease will be studied using two in vitro techniques: lymphocyte blastogenesis and the Jerne antibody-producing cell assay following in vitro immunization. Antigens will be prepared from two gram-positive bacteria, Actinomyces viscosus and A. naeslundii, and from a gram-negative bacteria: either Bacteroides melaninogenicuc or Liptothrichi buccalis. An unrelated antigen, sheep red blood cells (SRC), will also be tested in the two assay systems. The blastogenic responses of human peripheral blood, tonsil and spleen lymphocytes, and mouse lymphocytes to the bacterial antigens will be assayed to determine (a) the presence or absence of a population of antigen-sensitive cells and (b) the presence of mitogenic and/or antigenic component(s) of the bacterial preparations. Studies will be made of the ability of mouse spleen lymphocytes (a) to produce antibodies to an unrelated antigen, such as SRC, in the presence of a bacterial antigen and (b) to produce antibodies to the bacterial antigens, or antigen fractions. Human peripheral blood, tonsil and spleen lymphocytes will similarly be tested for their ability to produce antibodies. The information obtained in this study should help in understanding the role of bacteria in the induction and/or augmentation of a local immune response.